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Sediment Re-Sampling

(12/2/05) After Hurricane Katrina, USEPA collected sediment samples at more than 430 sites in the streets and public areas of Jefferson, Orleans, Plaquemines and St. Bernard Parishes. Each sediment sample was tested for fecal coliform bacteria and about 200 different chemicals including volatile organic compounds (VOC), semi-volatile organic compounds (SVOC), metals, pesticides, herbicides, polychlorinated biphenyls(PCBs), polycyclic aromatic hydrocarbons (PAH), and total petroleum hydrocarbons (TPH).

As expected in a densely populated urban area, a variety of chemicals were detected in the sediments. The most frequently detected chemicals included some metals, petroleum hydrocarbons, and PAHs, and to a lesser extent, pesticides. These levels are similar to the historical levels found in these parishes before Katrina and to other urban areas throughout the nation. The majority of chemicals detected were below levels of health concern. However, there were some localized areas with levels of arsenic, PAHs and diesel and oil range organics that exceeded both LDEQ Risk Evaluation/Corrective Action Program (RECAP) and USEPA's risk criteria based on long-term (30 years) residential exposure assumptions. LDEQ and USEPA revisited approximately 145 previous sediment sample locations where contaminant concentrations exceeded LDEQ and USEPA criteria. For re-sampling to occur, the sediment depth had to exceed a depth of 1.5 cm (0.5"). Sediments of sufficient depth were found at 14 locations, and were re-sampled to determine current conditions.

The results of the re-sampling were compared to LDEQ RECAP Standards (available at: http://www.deq.louisiana.gov/technology/recap/2003/index.htm). In Orleans Parish, 3 samples contained arsenic above the RECAP value of 12 ppm, with levels ranging from 14.4 to 17.6 ppm arsenic. One sample contained benzo[a] pyrene above the RECAP value of 0.33 ppm with a level of 0.77 ppm. Although the levels in these four samples exceed RECAP values, they fall within a risk range of 1 in 1,000,000 to 1 in 10,000 risk of an individual developing cancer over a lifetime from exposure to those concentrations, which EPA has found acceptable in other contexts. In St. Bernard Parish, one sample contained diesel range organics above the RECAP value of 650 ppm, with a level of 2100 ppm. USEPA and LDEQ believe the diesel range organics value is associated with the Murphy Oil Spill, which is currently being addressed by the responsible party with USEPA and LDEQ oversight. USEPA and LDEQ are working together to determine next steps.